A couple of corrections and additions. It appears that the family came to New Zealand in 1853, not 1851.  MAXWELLS ABOARD THE "CRESSWELL" - FROM LONDON TO NEW ZEALAND, 1853: A Mr. & Mrs J. Maxwell, accompanied by James Maxwell, William J. Maxwell and Hannah Maxwell departed from London on the "Cresswell" on 1 May 1853, arriving at New Plymouth (New Zealand) on 25 August, heading on to Auckland where they arrived on 6 September 1853. William John Maxwell appears to have served in the  Auckland Militia during the New Zealand Land Wars of the 1860s. William John Maxwell and Margaret Isabella Eales were married 8 Feb 1868 in Cook Street, Auckland (not Hawkes Bay) by Rev James M. Smith of the Scotch Presbytarian Church.  Margaret's father "the late Mr. Eales" was from Belfast, Ireland. They had a son (name unknown) born on April 2, 1870 at their residence at Freeman's Bay, Auckland, New Zealand. William's brother James may be the same James Maxwell, Storeman of Auckland, who married Matilda England (date unknown) and had a son, also called William John Maxwell.  William in turn married Annie Catherine Newbold 7 March 1886 in College Road, Ponsonby, Auckland.